The field of the invention relates generally to a filtration method and system for removing particulate matter from a gas turbine air intake, and more particularly, to a filtration method and system that includes filter elements and non-discharging electrostatic electrodes for removing particulate matter from the gas turbine air intake.
Fabric filtration is a common technique for separating out particulate matter in an air stream. Fabric filtration is often accomplished in a device known as a baghouse. Known baghouses include a housing that has an inlet for receiving dirty, particulate-containing air and an outlet through which clean air leaves the baghouse. The interior of the housing is divided by a tube sheet into a dirty air or upstream plenum and a clean air or downstream plenum, with the dirty air plenum in fluid communication with the inlet and the clean air plenum in fluid communication with the outlet. The tube sheet typically includes a number of apertures and supports a number of filter elements with each filter element covering one of the apertures.
Known filter elements can include a support structure and a fabric filter media. The support structure, which is also called a core, typically has a cylindrical shape and is hollow. The walls of the support structure may be similar to a screen or a cage, or may simply include a number of perforations, so that a fluid can pass through the support structure. The support structure has at least one end that is open and that is capable of being coupled to the tube sheet at an aperture. The support structure extends from the tube sheet into the dirty air plenum. There are several types of fabric filter media. A “bag” filter media is flexible and/or pliable and is shaped like a bag. A cartridge filter media is relatively rigid and pleated. The filter media is mounted around the exterior or outer portion of the support structure.
During use, as particulate matter accumulates or cakes on the filters, the flow rate of the air is reduced and the pressure drop across the filters increases. To restore the desired flow rate, a reverse pressure pulse is applied to the filters. The reverse pressure pulse separates the particulate matter from the filter media, which then falls to the lower portion of the dirty air plenum.
An electrostatic device, such as an electrostatic precipitator, can also be used for separating particulate matter from an air stream. In an electrostatic precipitator, particulate matter is electronically charged and then collected through the action of an electric field. An electrostatic precipitator includes a discharge electrode that is maintained at a high voltage and a non-discharge electrode that is maintained at a relatively lower voltage or at ground. As the particulate-containing air steam flows past the electrodes, the electric field present between the electrodes operates to charge a percentage of the passing particles and causes them to collect on the non-discharge electrode.